Some injection molded parts, for example plastic preforms of the variety that are for blow molding into beverage bottles, require extended cooling periods to solidify into substantially defect-free molded parts. To the extent that the cooling of the molded part can be effected outside of the injection mold by one or more post-mold holding devices then the productivity of the injection mold may be increased (i.e. lower cycle time). A variety of such post-mold holding devices, and related methods, are known and have proven effective at the optimization of the injection molding machine cycle time.
In a typical injection molding system, such as the system 10 depicted with reference to FIG. 1A, and as generally described in commonly assigned U.S. Pat. No. 6,171,541 (Inventor: NETER, Witold, et al.; Published: 9 Jan. 2001), just-molded, and hence partially cooled, molded articles 2 are ejected from the mold half 8, when the mold halves 8, 9 are spaced apart, and into molded article holders 50 (i.e. commonly known as a cooling tube, a take-off tube, or a cooling pipe, amongst others). The holders 50 are arranged on a molded article holding device 15 (i.e. commonly known as an end-of-arm-tool, carrier plate assembly, removal device, post-cooling apparatus, amongst others), the holding device 15 arranged to be cyclically positioned between an in-mold position, between the mold halves 8, 9, to receive the molded articles 2, and an out-board position, as depicted, to allow the mold halves 8, 9 to close and begin another molding cycle. Preferably, the molded articles 2 are held in the holders 50 until the molded articles 2 have cooled sufficiently that they may be ejected without risk of further deformation. While held in the holders 50, the cooling of the molded articles 2 may be assisted by the use of cooling/extraction pins 14 expelling a cooling fluid onto exposed portions of the molded articles 2. The cooling/extraction pins 14 are arranged on another molded article holding device 12 (i.e. commonly known as a COOLJET, a trademark of Husky Injection Molding Systems Ltd.), the holding device 12 arranged to be cyclically positioned between a cooling position, with the cooling/extraction pins 14 positioned adjacent the exposed portion of the molded articles 2, and an out-board position, as depicted. It is also known to use the cooling/extraction pins 14 to extract the molded articles 2 from the holders 50. The transfer of the molded articles between the holders 50 and the cooling/extraction pins 14 has been effected by various means. The steps involved in the typical transfer process include: (i) positioning the cooling/extraction pins 14 within a suitable region of the molded articles 2; (ii) connecting the cooling/extraction pins 14 to a negative pressure source, thereby creating a vacuum within the region of the molded articles 2; (iii) forcibly ejecting the molded articles 2 from the holders 50; once released from the holders 50, the molded articles 2 are captured by the cooling/extraction pins 14, under the applied vacuum, and the molded articles are extracted with the re-positioning of the holding device 12. The molded articles 2, extracted with the holding device 12, may then be re-handled and then ejected by the application of a positive fluid pressure through the cooling/extraction pins 14.
It is known to practice the step of forcibly ejecting the molded articles 2 from the holding device 15 by means of direct mechanical action, not shown. For example, commonly assigned U.S. Pat. No. 5,447,426 (Inventor: GESSNER, Dieter, et al.; Published: 5 Sep. 1995) describes a mechanically-actuated rail that bears against an outwardly extending portion of the molded articles, thereby forcing the molded articles from the holders. Such a means has proven to be a very reliable solution for ejecting the molded articles. However, not all molded articles have the requisite outwardly extending portion. In addition, such mechanical-based ejection systems do add significant weight to the holding device that requires larger driving motors to achieve the fast cycling speeds demanded by present productivity standards.
It has been known to configure the holder 50, as depicted with reference to FIG. 1B, to include a generally non-mechanical means for molded article ejection. In particular, the holder 50 includes a pressure channel 54 that is connectable to an air pressure source 18 via channel 18′, provided in a plate body 16. The pressure source 18 is configured to selectively provide overpressure or negative pressure through the pressure channel 54 to a cavity 52 defined along a tube 60 and tube insert 70. The pressure channel 54 includes a first portion, not shown, extending through the base of the tube, the first portion connecting a second portion, shown extending through a portion of the insert 70, with the pressure source 18′. The steps involved in the typical transfer process include: (i) configuring a suction air flow through the pressure channel 54 from the cavity 52 to the pressure source 18, the pressure source 18 configured as a negative pressure source, for effecting a transfer of the molded article 2 from the mold half 8 to the cavity 52; (ii) continuing the application of negative pressure through the pressure channel 54, to hold the molded article 2 in the cavity 52 of the holder 50, as the molded article 2 is cooled (by heat conduction through the tube 60 to a coolant circulating in the coolant channel 62 configured around the tube 60, and enclosed by a tube sleeve 64, the coolant channel 62 connectable to a coolant source 17, 17′ in the plate body 16); (iii) configuring the pressure source 18 to provide overpressure to the pressure channel 54, and thereby pressurize the cavity 52 and effect the ejection of the molded article 2 therefrom. Many factors affect the ejection of the molded article from the tube 2, including the geometry of the molded article 2 (e.g. a shallow draft angle on the outside of the molded article can cause the preform to stick in the tube). Suffice it to say, that not all of the molded articles 2 that are desired to be ejected simultaneously will release with common ease, and hence some molded articles may release earlier than others. Under such circumstances, when some subset of a total number of the molded articles are initially released, the cavity 52 of the corresponding holders 50 are at ambient pressure and hence the unchecked air flow from the pressure channel 54 is not being directed to the remaining holders 50 having molded articles 2 remaining therein. Accordingly, with the air flow losses associated with the venting holders 50, there may be insufficient air pressure remaining to dislodge the molded articles 2 that are more resistant to ejection in a timely manner, if at all.
FIG. 1B also shows that a fastener 72 is used to connect the holder 50 to the plate body 16, the holder configured to accommodate the fastener 72 along a passageway configured along a longitudinal axis of the holder 50. The foregoing arrangement while providing a readily serviceable connection, the technician merely needs to use a key through the pressure channel 54 to modify the connection, does have a significant drawback in that portions of the pressure channel 54, not shown, need to be off the longitudinal axis of the holder (namely the portion extending through the base of the tube 60). Accordingly, beyond the added complexity of manufacture, the foregoing arrangement does also suffer from a higher pressure drop between the pressure source 18 and the cavity 52.
Another example of a non-mechanical holder 150 is shown with reference to FIG. 2. The holder 150 is configured in much the same way as holder 50.
Wherever possible, similar features of the embodiments of the prior art and of the present invention have been given similar reference numbers and their descriptions have not been repeated.
The main difference between the two is that the holder 150 includes a checkable pressure channel 154, and an auxiliary pressure channel 136. The valve checkable pressure channel 154 includes a valve element 126 that is trapped between, at all times, a device portal 128 at the top of a portion of the pressure channel 154 that defines a valve chamber 124, and a plenum portal 130 configured at the base of the valve chamber 124. A valve seat 132 is configured adjacent the device portal 128 that cooperates with the valve element 126 for isolating the device and plenum portals 128, 130 when an overpressure is applied from the pressure source 118, 118′ to the pressure channel 154. The much narrower auxiliary pressure channel 136, relative to the pressure channel 154, is also connected to the pressure source 118, 118′, but without provision for a checkable valve. In addition, the insert 170 is configured to cooperate with the tube 160 and the fastener 72 such that it is movable along the longitudinal axis of the tube 160 to assist in supporting the molded article 2 as it is being ejected. The steps involved in the typical transfer process include: (i) configuring a suction air flow through both the pressure channel 154 (the valve element 126 resting in a configuration with respect to the plenum portal 130 such that the valve chamber maintains a fluid connection between the device and plenum portals 128, 130) and the auxiliary pressure channel 136, from the cavity 152 to the pressure source 118, the pressure source 118 configured as a negative pressure source, for affecting a transfer of the molded article 2 from the mold half 8 to the cavity 152; (ii) continuing the application of negative pressure through the pressure channels 154, 136, to hold the molded article 2 in the cavity 152 of the holder 150, as the molded article 2 is cooled; (iii) configuring the pressure source 118 to provide overpressure to the pressure channels 154, 136, the valve element 126 moving to cooperate with the valve seat 132, isolating the device portal 128 from the pressure source 118, as soon as air begins to flow into the cavity 152, the air flow through the auxiliary pressure channel 136 continuing unchecked (the auxiliary channel includes an outlet nozzle 138, which may assist in moving the insert 170 forward during ejection). The foregoing arrangement provides for reduced air pressure losses from empty holders 150, relative to the holder 50, the losses mitigated by the pressure losses through the relatively narrow auxiliary channel. Nonetheless, the auxiliary channel 136 and portions 154A and 154B of the pressure channel 154 are off-axis relative to a common connecting portion 154C of the pressure channel 154, with associated pressure losses which can affect the efficacy of the transfer from the mold 8 into the holder 150. Perhaps of more significance, is the pressure losses associated with the circuitous route in which the air must flow around the valve element 126 when effecting a suction air flow through the valve chamber 124. In particular, the device and plenum portals 128, 130 are arranged on opposite sides of the valve element 126 at all times thereby requiring the air to flow past the rather narrow gaps between the valve element and the valve chamber 124 and with associated pressure losses.
European Patent 1 123 189 B1 (Inventor: WEINMANN, Robert, et al.; Published: 29 Jan. 2003) provides yet another example of a non-mechanical variety of molded article holder that includes a pressure-biased valve check pin for controlling air flow between a cavity, defined in the holder, with a pressure source.